I was recently asked “how much cardio should you do? When do you worry about cardio raising your cortisol levels? And when do you worry about losing muscle?”

And I wish I had a simple answer like “3 times per week, for 30 minutes”, or “150 minutes per week.” But I don’t. It’s my usual answer of “it depends.

What does it depend on? A lot of factors, and that’s what we’ll cover in this article. But if you want to skip all the theory, and the figuring things out for yourself, our staff have done the work, taken the hard parts out of it for you, and can give you a solution that’s customized to you, on a silver platter. If you want to see whether you qualify to work with us, you can fill out this questionnaire.

So let’s get to it.

how much cardio should you do

Original source: here.

How Much Cardio Should You Do? The 4 Factors to Consider

What exactly does the amount of cardio you should do based on? What are the factors that need to be taken into consideration? In no particular order, here they are:

Factor #1: Your Goal

It comes as no surprise that someone whose goal it is to run a marathon should be doing way more cardio than someone whose goal is to build muscle.

So we have kind of a continuum, from least cardio, to most cardio. Here’s how I would organize this continuum:

  1. Trying to build muscle, and have a fast metabolism.
  2. Trying to build muscle, and have a slow metabolism.

One question I often get asked is “how much cardio should I do when trying to build muscle?” The answer is “if you have a fast metabolism: none.” If you have a slow metabolism, a bit more.

Moving on.

3. If you’re in a strength/power sport (like shot put, powerlifting, weight lifting, 100 meter sprinting, etc.), you should do very little, but slightly more than a person trying to gain muscle.

The reason that cardio should be minimized with the above 3 goals is that cardio and strength/power are diametrically opposed goals. You are really sending 2 opposite messages to the body. With strength training, the message is: build strength/muscle. With cardio, the message is: build endurance. Unfortunately strength and endurance are 2 opposite ends of the spectrum. After all, when was the last time that a marathoner won a 100 meter sprint? The answer: never. Also, when was the last time a sprinter won a marathon? The answer: also never.

While you can be pretty good at both, you can’t be world class at both. But most people reading this aren’t trying to be the best in the world at something.

4. If you’re trying to lose fat.

If fat loss is your goal, I wouldn’t worry too much about muscle losses. As long as you are doing strength training properly, and you’re consuming adequate protein, muscle losses will not be that big of a deal.

You should really only worry about muscle losses if you’re seriously trying to maximize every last bit of your genetic potential when it comes to muscle gain (a man can gain about 40-50 pounds of muscle, and it would take 4-5 years. A woman can gain about 20-25 pounds of muscle, and it would take about the same amount of time).

If you’re just trying to lose fat and get toned, muscle losses are not that much of an issue, again, on condition that you are strength training, and consuming adequate protein. I talk much more extensively about exercise for weight loss in this video.

5. If you’re in a mixed sport. Mixed sport, being where you need both power, and endurance. This would be sports like basketball, tennis, hockey, martial arts, etc.

These 2 (numbers 4 and 5) could really go in either order. Some people don’t require a lot of cardio to lose fat, and others do. Same with mixed sports. Some athletes naturally have a lot of endurance, and others don’t. Those with a lot of endurance don’t need to do as much cardio as those without much endurance.

6. If you’re in an endurance sport.

I grouped all endurance sports together, because yes, although there’s a vast difference in how much cardio you should do between a 5K, and a marathon, even the smallest distance that would be considered an endurance event would be more cardio than mixed sports.

I hate giving guidelines in terms of specific amounts, because a person’s goal is not the only factor that should be taken into account, but let me give it a shot (though notice that in some cases, the ranges will be VERY wide).

  1. Trying to build muscle, and have a fast metabolism: ideally, zero cardio. Nothing. The naturally skinny people already have a fast metabolism, and fairly low appetite (even though they swear up and down how much they eat). To add more calorie-burning activities when the goal isn’t to lose weight, but to gain it would be counterproductive. It’s like pouring water into a bucket that has a hole at the bottom. So this answers the question of “at what point should I be worried about losing muscle?” For this person, it would be right from the very beginning.
  2. Trying to build muscle, and have a slow metabolism: 2-4 days, of 20-40 minutes. This person can put on muscle, but there’s often some fat that comes along for the ride. To minimize the fat gain (it’s almost impossible to eliminate it), some cardio should be performed. So this really answers the question of “how often should I do cardio while weight training?
  3. People in strength/power sports: pretty similar to #2, above.
  4. Fat loss: zero, all the way up to 5-6 times per week for 45-60 minutes. This is where the wide variability comes in. We’ll elaborate on this in greater detail below.
  5. If you’re in a mixed sport: 3-6 times per week, for 20-60 minutes. Depends on both the sport, and the athlete.
  6. If you’re in an endurance sport: 4-6 times per week, for 30-60 minutes.

Factor #2: Your Hormonal Profile

I’ll assume that the majority of people reading this article are asking the “how much cardio should you do” question for the purpose of fat loss, more than the other 5 purposes, so I’ll elaborate on that one more than on the other ones.

This is really where the cortisol question comes in. Cortisol is the hormone we release more of when we’re under stress. We actually release it all the time, even when we’re not under stress, but we release more of it under short-term stress. If the stress is more long-term, the adrenal glands start to “burn out”, and we release less cortisol. Neither one is good: not low, not high cortisol.

So if you have issues with cortisol, you can still do cardio, but it should be of a low intensity. How low is low? Under 60% of your maximal heart rate. And what’s your maximal heart rate? The generally-accepted formula is 220 minus your age. So if you’re 50, your theoretical maximum would be 170. 60% of 170 is 102. So you want to do your cardio at an intensity that doesn’t exceed 102 beats per minute.

If you don’t have any problems with cortisol, just do whatever amount is appropriate for you.

The reason that you should decrease intensity when under stress is because different types of exercise stimulate different hormones.

For instance:

  • When you do steady-state cardio, you increase cortisol, decrease growth hormone, and decrease testosterone and estrogen
  • When you do interval training, you increase both cortisol and growth hormone, and testosterone and estrogen are pretty much unchanged
  • When you do strength training with moderate-high repetitions (10-20), moderate sets (2-4), and short rest periods between sets (30-90 seconds), you increase growth hormone, slightly increase cortisol, and no changes in testosterone and estrogen
  • When you do strength training with moderate-high sets (4+), low reps (under 7), high weights (over 80% of your max), and long rest periods between sets (3 minutes or more), you increase testosterone, don’t really change growth hormone, cortisol, or estrogen.

So as you can see, under stress, cortisol is already a problem, and doing prolonged cardio can drain even further an already drained body.

So take care of your cortisol levels first, and then resume cardio at the appropriate intensity and duration for your goals. I give you 7 stress-management strategies in this article.

Factor #3: Your Intensity

The trade-off for duration is intensity. You can do a lot of cardio, at a low-moderate intensity, or you can do a lot less for doing high intensity. What does “low, moderate, and high” really mean?

Low intensity is really anything under 60% of your maximal heart rate. Using out 50-year old as the example again, that would be less than 102 beats per minute. The intensity is not high enough to increase endurance, but it does have other benefits, like psychological, and immunological.

Moderate intensity is between 60-85%. So for our 50 year old, that would be 103-145 beats per minute. If your goal is fat loss, a good start at this intensity would be to aim to do it 3-4 times per week, for 30-45 minutes. Of course, you have to do strength training as well.

High intensity is anything over 85%. Again, for a 50-year old, that would be anything over 145 beats per minute. High intensity is really something that can only be maintained for only 1-4 minutes, before your speed drops. At this intensity, you only need to do it 2-3 times per week, for 20-30 minutes. Again, this is in combination with strength training. But be warned: if you haven’t done serious cardiovascular exercise in over 2-3 months, I wouldn’t start with high intensity. It might also be a good idea to get your doctor’s clearance in that case.

I cover more about the ratio of strength training to cardio in my article on exercise for weight loss.

Factor #4: Your Individual Response to Cardio

And the last factor that I can think of that really answers the question of “how much cardio should you do” is YOU. The X-Factor. As I mention over and over and over again, everyone is an individual, and there is a very wide variability of responses. One person may be able to lose fat just cutting back on calories, and strength training, whereas someone else may need to cut back on calories, do strength training, and cardio 5 times per week, for 30-60 minutes.

So ultimate, how do we know how much cardio per week to lose weight? First, we measure our clients, to know what their baseline is. Then, we might say they should do 3 times per week, for 30 minutes (that’s hypothetical. We give our best guess after getting ALL the necessary data from our clients). Then, after 2 weeks, we measure them again.

Because as I fully explain in my article on the importance of measurements, the way to really know how YOU specifically respond to any given exercise or nutrition program is to measure. We know how you SHOULD respond. But if we don’t measure, we don’t know how you DO respond. We know generally speaking how you should respond, but “generally speaking” is not good enough for us and our clients. We want specifics, and that’s where measurements are tremendously helpful.

If you’d like help in figuring this out for your own body, fill out this questionnaire, to see if you qualify to work with us.